1. Field of the Invention
The present invention relates to an image forming apparatus and an image forming method by which a printing operation can be performed while saving a toner consumption amount than in a normal case.
2. Description of the Related Art
In recent years, an image forming apparatus has been developed that has, in addition to a normal print mode to form and print a high-quality image, a toner save mode to perform a printing operation while saving a toner consumption amount than in a normal case. Methods for saving a toner consumption amount than in a normal case include a density conversion, a pulse width modulation, and the logical product of a normal print image and a culling pattern. However, even any of the toner save mode methods is desired to maintain the quality (readability) of the characters of an image with minimized deterioration. In order to realize this, there is a technique to extract an edge (contour) region of an image object such as a character or a line so that a toner consumption amount for the edge region in a save mode is equal to that in a normal print mode and regions other than the edge region provide a reduced toner consumption amount. This consequently achieves both of the character readability and the toner consumption amount saving (Japanese Patent Laid-Open No. 2011-131575).
On the other hand, in order to improve the print quality of black characters and lines, there is a technique to detect an edge region of an image object such as a black character or a line to expand the detected edge region (line width correction processing) (Japanese Patent Laid-Open No. 2000-206756).
A technique for the toner saving and a technique for the line width correction both require the edge detection of characters and lines in order to maintain and improve the print quality.
However, in the case of the above-described line width correction processing, an inputted pixel, which originally corresponded to an edge, is converted by the line width correction processing to a shape that does not correspond to an edge anymore. In a case where the above-described two techniques are realized by a parallel configuration, an edge region detected for the toner save processing is converted by the parallelly-provided line width correction processing to a shape that does not correspond to an edge region anymore. Thus, a disadvantage is caused in which an unnatural edge processing deteriorates the print quality. Specifically, in the case of the parallel configuration in which the toner save processing unit and the line width correction processing unit are executed in parallel, two processing units receive, as an input, an image prior to being subjected to the respective processings. Thus, the line width correction processing plumps the edge region but an original edge region before plumping is not subjected to toner saving, thus resulting in an unnaturally-highlighted edge.
In the case of a sequential configuration in which the line width correction processing is followed by the toner save processing, the above-described unnatural edge processing can be avoided. However, the two processings cannot share a buffer for edge detection, thus disadvantageously causing an increased circuit size. Specifically, in the case of the sequential configuration, the buffer used by the respective image processings cannot be shared, thus requiring a plurality of buffers to be independently configured for the respective image processings.